The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
An airplane is moved by several turbojet engines each housed in a nacelle also accommodating a set of additional actuating devices linked to its operation and providing diverse functions when the turbojet engine is in operation or at a stop.
These additional actuating devices comprise, in particular, a mechanical thrust reversal system.
More particularly, a nacelle usually exhibits a tubular structure comprising an air inlet upstream of the turbojet engine, a median section intended to surround a fan of the turbojet engine, a downstream section accommodating the thrust reversal means and intended to surround the combustion chamber of the turbojet engine and, usually terminated by an ejection nozzle located downstream of the turbojet engine.
This nacelle is intended to accommodate a dual flow turbojet engine able to generate by means of the blades of the fan in rotation a hot air flow, from the combustion chamber of the turbojet engine, and a cold air flow circulating outside the turbojet engine through an annular stream.
The thrust reversal device is, during landing of the aircraft, intended to improve the braking capacity of the latter by redirecting towards the front at least part of the thrust generated by the turbojet engine.
In this phase, the thrust reversal device obstructs the stream of cold air flow and redirects the latter towards the front of the nacelle, thereby generating a counter-thrust which adds to the braking of the wheels of the aircraft, the means implemented for achieving this reorientation of the cold air flow vary according to the type of reverser.
Different types of thrust reversal devices are usually known.
Another form of the latter provides that it comprises at least one element moveable between a closing position and an opening position cooperating in opening position to the production of the thrust reversal and at least one set of electromechanical maneuvering members for maneuvering the moveable element between the closing and opening positions.
The movable element may be, in non-limiting examples, a cowl of a nacelle, doors and/or reversal flaps upstream or downstream of the cowl of the nacelle.
As for the set of electromechanical maneuvering members, it comprises, substantially electric actuators intended to actuate the moveable elements and at least an electric bolt, called primary bolt intended to provide that they are maintained in retracted position and prevent any accidental deployment.
More particularly, the thrust reversal device is provided with three locking defense lines.
The set of electromechanical maneuvering members for maneuvering the moveable elements between their closing and opening positions of the thrust reverser are actuated by at least one electric turning machine according to the design of the system.
Moreover, the locks are reinforced by mechanical braking means controlled electrically, hydraulically or other.
Such braking means provide the blocking of the electric turning machine, in the event of loss of control of the latter or of the corresponding electromechanical member.
These mechanical braking means are, in particular, suited to protect from any overspeed of the electric turning machine and, thus, to have an additional security in the event of failure of this machine.
The mechanical braking means used may be, for example, a failsafe static brake using a technology of multiple disk brake type, a return spring brake and/or electrical unlocking control by an integrated linear actuator.
However, by mechanically blocking the motor at full speed, there is a risk of mechanically damaging the associated actuator.
In addition, such mechanical brakes are subject to rapid wear of the corresponding disks.
Furthermore, such mechanical brakes are heavy, bulky, complicated to implement and often expensive.